Survival and retention of Eschenchia coli O157:H7 and Campylobacter in contrasting soils from the Toenepi catchment

Abstract

The effect of soil type on transfer of zoonotic bacteria to rural streams was investigated using intact cores and turfs of Topehaehae gley soil and Kereone sandy loam. Simulated farm dairy effluent, containing laboratory grown Escherichia coli O157:H7 and Campylobacter, was added to cores and turfs that were stored at 10°C. Bacterial survival was measured in cores over 28 days. Simulated rainfall was applied at 25 and 50 mm h^‐1 to allow measurement of bacterial transfer to drainage (over 28 days) or surface runoff (at 7 days). Although both bacteria survived for 28 days, Campylobacter declined faster than E. coli O157:H7 with no differences identified for soil type. For Topehaehae soil there was little change in retention of E. coli O157:H7 over the 28 days for both rainfall rates, but there was an increase in retention over time for Kereone. In contrast there was an increase in retention of Campylobacter in both soils at either of the rainfall rates. When surface runoff was measured, less than 1% of each of the applied bacteria was recovered from either soil irrespective of rainfall rate. These findings suggest that rainfall will transfer faecal bacteria from gley soils bordering a stream to the water for at least 28 days after deposition.

Keywords:

• gley soil
• rural stream
• sandy loam soil
• zoonosis